Ultrasound has received widespread acceptance as a useful diagnostic tool by providing an image of the internal area of inquiry by emission of very high frequency sound waves from a transducer (commonly called a “probe”) placed in contact with the patient's skin adjacent that area of inquiry. Repeated arrays of ultrasonic beams scan that area and are reflected back to the transducer, where the beams are received and the data transmitted to a processing unit. A processing unit, to which the probe is connected, analyzes the information and composes a picture for display on an associated monitor screen. For some applications the determination of the precise position or location of the probe in real time with respect to the patient's body is desirable, e.g., to correlate, register or “fuse” the ultrasonic image to other scans (digital image sets), such as CT scans, MR scans, PET scans, and the like. This real time correlation matched with targeting software can be combined with real time tracking and navigation systems and devices to navigate an instrument within a patient for minimally invasive procedures. In other settings such as CT, when ultrasound is not available or useful virtual navigation of an instrument within a patient also may be image-guided by having the images registered to the patient using fiducial markers and also registered to a navigation and tracking device or system using recently acquired volume images (data sets) that are then co-registered to both the images and the navigation system.
Optical and electromagnetic tracking (EMT) technologies are two non-mechanical, real-time, approaches for accurate instrument tracking and navigation using appropriately registered volume images (digital data sets). Both optical and electromagnetic technologies have advantages and limitations, but on balance the technological advantages of EMT for minimally invasive procedures are dominant. In particular, EMT is believed to be the preferable technology because of the ability to track objects inside the body (beyond line-of sight) and the compact size of the tracked sensors. These powered sensors typically provide position and orientation data sets of 5 or 6 degrees-of-freedom (DOF) and combined with the electronic cables required are relatively expensive.
EMT systems that support image fusion and instrument tracking are commercially available and disclosed in the patent literature. They typically enable determination of 5 or 6 DOF orientation and position of an instrument, such as a needle, by determining location, orientation, and/or positioning information relative to some coordinate system. For example, Ascension Technology Corporation makes 5 and 6 DOF position and orientation tracking devices suitable for various medical applications, e.g., to navigate, localize, and guide medical instruments for image-guided procedures. Other manufacturers/suppliers of EM tracking systems include Polhemus, Inc. Northern Digital Inc. and Medtronic, Inc. Suppliers of software, tracked needles and other instruments for clinical use that utilize these technologies in medical procedures include Traxtal Corporation and Veran Medical. Image fusion in combination with ultrasound is available from Traxtal, Inc., GE Healthcare Ultrasound and Esaote Ultrasound, among others.
Typically these tracking systems use the attenuation of oriented electromagnetic signals to determine the absolute position and orientation of a sensor, relative to a source, e.g., a magnetic field generator. The source and the sensor are connected via cables to an electronics module, which contains a microcomputer and associated electronics of the system. The source typically includes three orthogonal coils that are pulsed in rotation, one after another. Each pulse transmits a radio frequency electromagnetic signal that is detected by the sensor. The sensor also contains two or three orthogonal coils, which measure the strength of the signal from the current source coil. By using the known pulse strength at the source and the known attenuation of the strength with distance, the position and orientation of the sensor coils can be calculated by the system via triangulation techniques.
Utilizing EM sensors with ultrasonic probes can be accomplished by permanently mounting the sensor(s) on the probe or by building such sensor(s) into the probe. However, the permanent mounting approach may not be desirable if the probe is also intended to be used in applications wherein its position need not be determined. Also, the inclusion of such sensor(s) permanently on or in the probe will likely increase the cost, complexity and service requirement of the probe. Therefore external attachment, when needed, has become the commercially dominant approach. The challenge in this case is to locate and attach, when required, the removable sensor(s) to the probe in a way that that is quick, secure and ergonomic. Thus, the use of some releasable mounting system has become a required element for registration and fusion of volume image data sets from CT, MR, PET, etc. for use during real time ultrasound imaging. This has been done by several companies to date, including GE Healthcare Ultrasound, Hitachi and Esaote Ultrasound.
In U.S. patent application Ser. No. 12/111,387, filed on Apr. 29, 2008, entitled “Bracket for Mounting At Least One Position Detecting Sensor On An Ultrasonic Probe”, which is assigned to the same assignee as this invention and whose disclosure is incorporated by reference herein, there is disclosed a bracket for use with an ultrasound transducer to releasably mount at least one sensor of a location/tracking system on the transducer and serves as one unique solution to fulfill this commercial ideal.
Other medical components or devices making use of EM sensors have been provided as part of an EMT system for use with EM tracked ultrasound transducers and also may be used in properly registered CT or CT fused with PET or MR image sets without ultrasound. These devices include needles of all types, fiducial markers with EMT sensors embedded to aid with patient and image data registration, and other tracked devices. These tracked devices, especially the needles with sensors in the tip, have been shown to have great advantages for simplifying the safe and accurate placement of these instruments during minimally invasive procedures. However, to date most devices and all existing needles using EM tip sensors have the sensor(s) permanently attached and must be discarded after a single use or require time and expense to re-process and re-sterilize. In most cases the cost of these disposable devices makes the routine use of EM tracking and navigation cost-prohibitive. Thus, until now, expense has been a serious limiting factor to general adoption of EM technology for image guidance.
The subject invention entails a complete mechanical tool set that will allow re-use of all the expensive sensor components of an EMT system to greatly reduce costs per procedure in the rapidly expanding market for image fusion and guidance. While re-using the expensive 5 and 6 DOF powered (active) EM sensors will require a more complex setup and assembly process for each use, the payoff in reduced cost per procedure is believed to be so critical that the small extra time required for such set-up will be gladly tolerated.
The complete EMT tool set for providing image guidance in ultrasound applications and for other imaging modalities includes not only the subject matter of this invention (which will be described shortly), but also dedicated system software. It is anticipated that most of such registration, navigation and image fusion software will be developed and supplied by the original equipment manufacturers of the imaging hardware.
The system of this invention is in the form of an image fusion and navigation tool set that includes a number of components. Foremost among those components is a specially designed needle (trochar) with a reusable EM sensor in the tip of the stylet. Other components include, a specially designed ultrasound bracket to accept one or more reusable EM sensor(s) and a needle guide (e.g., a slotted needle guide enabling mechanical positioning of the linear instrument within the image plane of the ultrasound transducer). In addition, the subject tool set includes a releasably securable adapter device for mounting a reusable EM sensor on any needle or elongated medical instrument (e.g., biopsy needles, syringes, ablation needles, (cryoprobes, RF probes, catheters containing a stylet, etc.)) to convert that instrument into an EM trackable instrument (which will be accurate in the absence of bending/deflection beyond the attachment point of the device), and skin surface markers for facilitating three dimensional image registration and image fusion in certain circumstances (e.g., these may not be useful in cases where ultrasound is used because more accurate registration may be achieved using internal anatomic landmarks visible on real time images). Those markers can be either the passive or active types. Passive type markers are typically sterile adhesive devices that contain only a radio-opaque marker and/or a marker visible on MR imaging. The passive markers of this invention also include a keying feature for registration using an EM sensor (contained within a housing). Active type skin surface markers are typically non-sterile adhesive devices with embedded or attached EM sensors that can with proper software support provide continuous real-time automatic registration updates for image fusion and navigation. Traxtal, Inc. and Veran Medical Technologies provide skin surface markers with embedded EM sensors, while the present invention proposes skin surface markers with attachable EM sensors. In accordance with one aspect of the present invention in order to provide active markers, passive markers are supplemented with a mounting bracket that is adapted to receive a reusable EM sensor. In addition to the foregoing, it is anticipated that the EMT tool set will also include custom sterile disposable cover/drape packages to allow sterility and re-use without reprocessing of the expensive EM sensors and connecting cables.
The EMT tool set of the subject invention is intended to support any EM technology and function with all imaging modalities alone or in combination (fusion). In particular, the components of the subject invention will enable CT, PET-CT, or MR image fusion with or without a real-time ultrasound image and 5 or 6 DOF navigation within the EM field. Properly applied, the technology of this invention will allow better visualization of target lesions in the body and highly accurate instrument navigation to reach them more quickly and safely. In particular, it is anticipated that the subject invention will be used by the full spectrum of clinicians that employ image guidance for reaching internal targets within a patient.
The subject invention's image fusion and navigation tool set is designed with a universal approach allowing components to be used across all OEM imaging platforms. It is anticipated that the subject invention will be utilized by physicians in the following specialties: interventional radiology, radiology, surgery and cardiology. Anticipated clinical applications are biopsy procedures, ablation procedures, catheter placements, intravascular procedures and endoscopic procedures.
All references cited and/or identified herein are specifically incorporated by reference herein.